Currently, I have an AirPort Express which gives 802.11/b/g access to my cable modem, and a MacBook that has 802.11/n. If I add an Apple TV, which does 802.11/n, what speed will it transfer/stream from the MacBook at, the "n" speed they both have, or the "g" speed of the AirPort Express? There's no Internet involved, so I'd guess "n", but am I right?

Put another way, if I add an Apple TV, do I also need to upgrade to an AirPort Extreme base station to give the MacBook/Apple TV "n" speed?

actually I would have guessed at the "g" speed. The content will only be able to be transferred at the Macbooks fastest speed. I think of it like this, The macbook sends the info to the express at "G" speed so the Airport Express can only send it to the ATV at "g" speeds. . .

Currently, I have an AirPort Express which gives 802.11/b/g access to my cable modem, and a MacBook that has 802.11/n. If I add an Apple TV, which does 802.11/n, what speed will it transfer/stream from the MacBook at, the "n" speed they both have, or the "g" speed of the AirPort Express? There's no Internet involved, so I'd guess "n", but am I right?

The Airport Express doesn't support 802.11n. Plus, if you have one 802.11g device connected to your 802.11n network, the rest of the 802.11n devices will slow down. Am I missing something here?

Currently, I have an AirPort Express which gives 802.11/b/g access to my cable modem, and a MacBook that has 802.11/n. If I add an Apple TV, which does 802.11/n, what speed will it transfer/stream from the MacBook at, the "n" speed they both have, or the "g" speed of the AirPort Express? There's no Internet involved, so I'd guess "n", but am I right?

The Airport Express doesn't support 802.11n. Plus, if you have one 802.11g device connected to your 802.11n network, the rest of the 802.11n devices will slow down. Am I missing something here?

Yes. Does the machine stream directly to the Apple TV or does it go through the Airport Express?

Grover is correct. Unless you create a "Computer-to-Computer" (Apple's term for adhoc) network, your router will be handling all traffic, therefore operating at whatever speed it operates at.

Even if you upgrade the router to an 802.11n capable Airport Extreme, if an 802.11g device joins that network (like an Airport Express), the overall network speed will slow to 802.11g speeds. You can avoid this by running an ethernet cable from the Airport Extreme to the Airport Express, and disabling the Express' wireless system (or have it create it's own separate network). USB printer sharing and AirTunes will continue to work. Of course, this assumes you actually can run a cable between the two._________________MacBook Pro 1.83GHz Core Duo, 2GB RAM, 250GB HD, Dell 802.11n card, 1.4TB external
MacBook 1.83GHz Core Duo, 2GB RAM, 60GB HD
iMac 1.83GHz Core Duo, 2GB RAM, 160GB HD, 1TB external, EyeTV Hybrid

You can bypass your wireless 802.11b/g router with Internet Sharing. This will let you take full advantage of 802.11n between a Mac with 802.11n and the Apple TV. You just need to go into System Preferences -> Sharing. Highlight Internet Sharing and select share from Ethernet (you'll still need this connection) to computers using Airport. Once you turn it on, go to your Apple TV and select the network in settings. There is a drawback though. AirPort cards typically have a weaker outgoing signal than a your average router. Things could get sketchy the further you get away from your Apple TV.

Or maybe not... The transfer rate shown on my Mac is in excess of the cable provider's nominal speed, and also in excess of its "turbo" speed, though not by much, and VERY consistent. So, maybe it IS doing Mac to AirPort Express to Apple TV internally, so a faster AirPort would help. Ah, decisions, decisions...

Currently, I have an AirPort Express which gives 802.11/b/g access to my cable modem, and a MacBook that has 802.11/n. If I add an Apple TV, which does 802.11/n, what speed will it transfer/stream from the MacBook at, the "n" speed they both have, or the "g" speed of the AirPort Express? There's no Internet involved, so I'd guess "n", but am I right?

.... Plus, if you have one 802.11g device connected to your 802.11n network, the rest of the 802.11n devices will slow down. Am I missing something here?

this is not correct. one of the major improvements of "N" is that "G" devices will *not* slow down "N" devices when used on the same network.